Electronic shift on the fly part-time electro mechanical transfer case

ABSTRACT

A transfer case comprising an input shaft and a first output shaft sharing a primary axis of rotation; a second output shaft offset from the first output shaft; a range shifter comprising a first cam constructed and arranged to selectively shift a vehicle to a high-range drive mode, a low range drive mode, or a neutral drive mode; a mode shifter comprising a second cam constructed and arranged to actuate a synchronizer which selectively shifts the vehicle between a two-wheel drive and a four-wheel drive mode; and a dual drive gear interposed between the range shifter and the mode shifter which is rotatable to actuate the first cam and the second cam.

TECHNICAL FIELD

The field to which the disclosure generally relates to includes transfercases.

BACKGROUND

A vehicle may include an electronic shift on the fly transfer case whichmay allow for the selective engagement of a four-wheel-drive mode or atwo-wheel-drive mode.

SUMMARY OF ILLUSTRATIVE VARIATIONS

A number of variations may include a transfer case comprising: an inputshaft having a primary axis of rotation; a first output shaft which isconcentric with the input shaft; a second output shaft offset from thefirst output shaft; a range shifter comprising a first cam rotatableabout the primary axis constructed and arranged to selectively shift avehicle to a high-range drive mode, a low range drive mode, or a neutraldrive mode; a mode shifter comprising a second cam rotatable about theprimary axis constructed and arranged to actuate a synchronizer whichselectively shifts the vehicle between a two-wheel drive and afour-wheel drive mode; and a dual drive gear interposed between therange shifter and the mode shifter, wherein a first side of the dualdrive gear includes an actuating tab constructed and arranged to actuatethe first cam and wherein the second cam is attached to a second side ofthe dual drive gear so that the mode shifter is activated by rotation ofthe dual drive gear.

A number of variations may include a transfer case comprising: an inputshaft having a primary axis of rotation; a first output shaft which isconcentric with the input shaft; a second output shaft offset from thefirst output shaft; a range shifter comprising a first cam, a firstshift fork, wherein the first shift fork is driven axially by the firstcam, and a first sleeve which is axially driven by the first shift fork;a mode shifter comprising a second cam, a second shift fork, wherein thesecond shift fork is driven axially by the second cam, and asynchronizer, wherein the synchronizer is actuated by the second shiftfork through rotation of the second cam; and a dual drive gear, whereinthe dual drive gear is rotated in a forward and a reverse direction toactuate the range shifter and the mode shifter.

A number of variations may include a method for assembling a transfercase comprising: providing an input shaft and a first output shaftcoaxially on a primary axis of rotation; providing a second output shaftoffset from the first output shaft; providing a power transmissiondevice interposed between the first output shaft and the second outputshaft; providing a range shifter operatively attached to the firstoutput shaft comprising a first cam constructed and arranged forshifting between a low-range drive mode, a high-range drive mode, and aneutral drive mode; providing a mode shifter for shift-on-the-flycomprising a second cam operatively attached to a synchronizerconstructed and arranged for shifting between a two-wheel drive mode anda four-wheel drive mode; providing a dual drive gear between the rangeshifter and the mode shifter constructed and arranged so that rotationof the dual drive gear actuates the range shifter and the mode shifter;and providing a gear train off axis from the primary axis constructedand arranged to drive the dual drive gear in a clockwise and counterclockwise direction.

Other illustrative variations within the scope of the invention willbecome apparent from the detailed description provided hereinafter. Itshould be understood that the detailed description and specificexamples, while disclosing variations of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Select examples of variations within the scope of the invention willbecome more fully understood from the detailed description and theaccompanying drawings, wherein:

FIG. 1 illustrates a schematic of a vehicle including a transfer caseaccording to a number of variations.

FIG. 2 illustrates an exploded view of a range shifter according to anumber of variations.

FIG. 3 illustrates a perspective view of an electric motor and a geartrain according to a number of variations.

FIG. 4 illustrates an exploded view of a mode shifter according to anumber of variations.

FIG. 5 illustrates a section view of a transfer case according to anumber of variations.

DETAILED DESCRIPTION OF ILLUSTRATIVE VARIATIONS

The following description of the variations is merely illustrative innature and is in no way intended to limit the scope of the invention,its application, or uses.

Referring to FIG. 1, in a number of variations, a vehicle 30 may includean engine 32, including, but not limited to, an internal combustionengine which may be operatively connected to a power transmission device34 which may be operatively connected to a rear driveline 36 and a frontdriveline 50. The power transmission device 34 may generate and delivertorque from the engine 32 to the rear driveline 36 and the frontdriveline 50. In a number of variations, the rear driveline 36 mayinclude a rear drive shaft 38. A first end 40 of the rear drive shaft 38may be operatively connected to a rear differential 44 which may beoperatively connected to a rear axle 46. A pair of rear wheels 48 may beattached to opposing ends of the rear axle 46. A second end 42 of therear drive shaft 38 may be operatively connected to and may be driven bya first output shaft 86 of an electro mechanical transfer case (EMTC)84. The EMTC 84 may be operatively connected to an input shaft 90 whichmay be operatively connected to the power transmission device 34. TheEMTC 84 may be used to selectively engage a four-wheel drive mode or andtwo-wheel drive mode of the vehicle 30 as well as to selectively put thevehicle 30 into a high or low range mode. The EMTC 84 may be operativelyattached to a reversible electric motor 76. The EMTC 84 may also includea second output shaft 88 which may be operatively connected to the frontdriveline 50. In a number of variations, the front driveline 50 mayinclude a front drive shaft 52 which may be operatively connected to thesecond output shaft 88 of the EMTC 84 and may be driven by the secondoutput shaft 88. The front driveline 50 may also include a frontdifferential 54 which may be operatively connected to the front driveshaft 52 and a front axle 56. A pair of front wheels 58 may be attachedto opposing ends of the front axle 56.

FIGS. 1-5 illustrate a number of variations. In a number of variations,the EMTC 84 may include a range shifter 98 which may be used to shiftthe vehicle 30 to a low-range drive mode, a high-range drive mode, or aneutral drive mode, variations of which are illustrated in FIGS. 2 and5. The EMTC 84 may also include a mode shifter 148 which may be used toengage a two-wheel drive mode and a four-wheel drive mode, variations ofwhich are illustrated in FIGS. 4 and 5. In a number of variations, therange shifter 98 and the mode shifter 148 may be mounted coaxially alonga primary axis 96, a variation of which is illustrated in FIG. 5. In anumber of variations, a gear train 60, which may be off axis or offsetfrom the primary axis 96, may be used to rotate a dual drive gear 62which may be mounted concentric to the range shifter 98 and the modeshifter 148 around the primary axis 96, and may be used to actuate therange shifter 98 and/or the mode shifter 148, a variation of which isillustrated in FIG. 3. The gear train 60 may include a plurality ofgears 72, 74 which may also be constructed and arranged to be rotated ina clockwise or counterclockwise direction. In one variation, the geartrain 60 may include an input gear 72 and an intermediate output gear74. The intermediate output gear 74 may be driven by the input gear 72.The intermediate output gear 74 may drive and rotate the dual drive gear62. In a number of variations, a reversible electric motor 76, which mayalso be off axis from the primary axis 96, may be operatively connectedto the gear train 60 and may be used to control the rotation of the dualdrive gear 62 in a clockwise or counterclockwise direction. In a numberof variations, an electronic control unit (ECU) 78 may be operativelyconnected to the reversible electric motor 76 and may be used to controlthe rotation of the dual drive gear 62, a variation of which isillustrated in FIG. 1. The ECU 78 may be operatively connected to atleast one sensing element 80 which may detect a position of the dualdrive gear 62. In one variation, the at least one sensing element 80 maybe located on a peripheral surface of the dual drive gear 62, avariation of which is illustrated in FIG. 4, and may be mechanical orelectrical. The ECU 78 may then automatically signal the reversibleelectric motor 76 to drive the dual drive gear 62 in response to thedetected position of the dual drive gear 62 by the at least one sensingelement 80 for actuating movement of at least one of the range shifter98 or the mode shifter 148.

Referring to FIG. 1, in one variation, the ECU 78 may be constructed andarranged to operate in an automatic drive mode which may automaticallycontrol the reversible electric motor 76 to control whether the vehicle30 is in a four-wheel drive mode or a two-wheel drive mode. A driver maythen manually select whether the vehicle 30 is in high-range orlow-range through a range selection device 81 which may be accessible tothe driver. In another variation, the ECU 78 may be constructed andarranged so that a driver may manually select one of the available drivemodes and ranges through a mode/range selection device 82 which may beaccessible to the driver. In another variation, the ECU 78 may beconstructed and arranged so that a driver may choose whether the ECU 78automatically chooses the drive mode setting or whether the driver maymanually choose the drive mode or the range mode through the range/modeselection device 82. The ECU 78 may process and relay control signals tothe EMTC 84 to cause the EMTC 84 to actuate the range shifter 98 and/orthe mode shifter 148 in response to the at least one sensing element 80and/or the detected position of the dual drive gear 62. In a number ofvariations, the ECU 78 may be part of or may be a general purpose orspecific purpose computer.

Referring to FIG. 5, in a number of variations, the EMTC 84 may includean input shaft 90, as discussed above, which may be constructed andarranged to be driven by the power transmission device 34. The engine 32may rotate a drive shaft which may be coupled to the power transmissiondevice 34 which may convert the output power from the engine 32 to ageared output drive power. The output drive power from the powertransmission device 34 may be transmitted to the input shaft 90 of theEMTC 84. The EMTC 84 may then selectively transmit output drive power tothe front wheels 58 and/or the rear wheels 48. In a number ofvariations, the EMTC 84 may include a housing 92 which may surround atleast a portion of the range shifter 98, the mode shifter 148, and thedual drive gear 62. The housing 92 may also include various seals,recesses, shoulders, flanges, bores, etc. which may be constructed andarranged to position and accept various components of the EMTC 84. In anumber of variations, the first output shaft 86 and the second outputshaft 88 may extend within a portion of the housing 92 and may berotatable within the housing 92. In a number of variations, a portion ofthe input shaft 90 may also extend within the housing 92 and may berotatable within the housing 92 and may be supported by one or morebearing assemblies 94. In a number of variations, the input shaft 90 maybe coaxial with the first output shaft 86. Any number of suitabledevices may be used to transfer torque between the first output shaft 86and the second output shaft 88 including, but not limited to, a belt, achain, or a gear train.

Referring again to FIG. 5, in a number of variations, the input shaft 90may be rotatable around a primary axis 96 of rotation. The range shifter98 and the mode shifter 148 may be positioned coaxially with the inputshaft 90 and may be spaced longitudinally adjacent from each other,which may allow for the use of fewer off-axis components to perform theshifting functions of the range shifter 98 and the mode shifter 148. Thedual drive gear 62 may also be coaxial with the input shaft 90 and maybe interposed between the range shifter 98 and the mode shifter 148. Thedual drive gear 62 may be constructed and arranged so that it may beconfigured for reversible clockwise and counterclockwise rotation aboutthe primary axis 96 through an angular arc of less than 360 degrees. Thedual drive gear 62 may be constructed and arranged so that during afirst end portion of angular rotation about the primary axis 96, thedual drive gear 62 engages and operates the range shifter 98 and duringa second opposite end portion of angular rotation about the primary axis96, the dual drive gear 62 actuates the mode shifter 148.

Referring to FIGS. 2 and 5, in a number of variations, a first side 68of the dual drive gear 62 may be operatively connected to the rangeshifter 98 and may be used to shift the range shifter 98 to a low-rangedrive mode, neutral drive mode, or a high-range drive mode throughrotation of a barrel cam 100. In a number of variations, the barrel cam100 may include a barrel tab 102. The barrel tab 102 may include a firstportion 104 which may extend radially outward from the outer perimeterof the barrel cam 100 and a second portion 106 which may extend axiallyfrom the first portion toward the dual drive gear 62, a variation ofwhich is illustrated in FIG. 2. The barrel tab 102 may be constructedand arranged to be actuated by an actuating tab 64 on the dual drivegear 62, as will be discussed hereafter. In a number of variations, thebarrel cam 100 may include a cam surface groove 108 which may extendcircumferentially and axially along an interior surface of the barrelcam 100 to define an axial range shift movement in response to rotationof the barrel cam 100. In a number of variations, the cam surface groove108 may include a first end portion 110, a second end portion 112, andan intermediate portion 114 extending therebetween. The first endportion 110 may include a predetermined circumferential arcuate lengthand may lie in a first plane perpendicular to the primary axis 96. Thesecond end portion 110 may include a predetermined circumferentialarcuate length and may lie in a second plane perpendicular to theprimary axis 96 spaced from the first plane. The intermediate portion114 of the cam surface groove 108 may extend arcuately and axiallybetween the first end portion 110 and the second end portion 112 todefine axial shifting movement of a shift fork 116 between the low-rangeand high-range drive mode, as will be discussed hereafter. The barrelcam 100 may be rotatable about the primary axis 96 through an arc ofless than 360 degrees in response to rotation of the dual drive gear 62in either rotational direction.

In a number of variations, the range shifter 98 may also include a shiftcollar 126 which may include an axial groove 128 which may allow passageof a first and second pin 122 of the shift fork 116 to move radiallyinto engagement within the cam surface groove 108 of the barrel cam 100for driving axial travel of the shift fork 116 in response to rotationof the barrel cam 100. The shift fork 116 may act as a cam followertraveling within the cam surface groove 108 of the barrel cam 100 as thebarrel cam 100 is rotated in either rotational direction. The shift fork116, barrel cam 100, and shift collar 126 may surround an axiallymoveable and rotatable internal range sleeve 130. The internal rangesleeve 130 may include a groove 132 which may be engageable with aprotrusion 124 on the inner surface 120 of the shift fork 116 which mayallow for rotation of the internal range sleeve 130 relative to theshift fork 116. In one variation, the shift collar 126 may comprise acylindrical element which may support the shift fork 116 through theaxial groove 128 which may allow for guided axial movement of the shiftfork 116 and may prevent rotational movement of the shift fork 116. Theshift collar 126 may allow the shift fork 116 to slide in an axialdirection to drive the internal range sleeve 130 in response to shiftingrotational movement of the barrel cam 100 between a low-range angularposition, neutral angular position, and a high-range angular position.

Referring to FIG. 5, in a number of variations, the internal rangesleeve 130 may be engageable between the range shifter 98 and a gearreduction assembly 138 to the first output shaft 86 through a splinedconnection which my allow for axial movement of the internal rangesleeve 130 with respect to the first output shaft 86. The gear reductionassembly 138 may vary the drive power between the input shaft 90 and thefirst and the second output shaft 86, 88. In a number of variations, thegear reduction assembly 138 may include a planetary gear assembly 212which may include a plurality of planetary gears 214 which may beoperatively attached to a gear carrier 216. The plurality of planetarygears 214 may rotate within a ring gear 218 and may be driven by a sungear 220. In a number of variations, when the shift fork 116 is driveninto a low-range drive mode portion of the cam surface groove 108, theinternal range sleeve 130 may axially move to couple the first outputshaft 86 with the planetary gear carrier 216. When the shift fork 116 isdriven into a high-range drive mode portion of the cam surface groove108, the internal range sleeve 130 may axially move to couple the firstoutput shaft 86 with the sun gear 220. The gear teeth 222 of theinternal range sleeve 130 may engage with the internal teeth 224 of thesun gear 220. The sun gear 220 may be driven by the input shaft 90. Theplurality of planetary gears 214 may be rotatable around the sun gear220 and may be driven by the sun gear 220. Drive torque may betransferred to the first output shaft 86 directly from the sun gear 220or indirectly through the planetary gear carrier 216 depending on thedrive ratio desired. The gearing ratio between the sun gear 220 and theplurality of planetary gears 214 may be a reduction ratio, rotating thefirst output shaft 86 at a different speed than the input shaft 90. In anumber of variations, the reduction ratio may be in a range betweenapproximately 1:1 to approximately 10:1, inclusive, with a preferredratio of approximately 2.6:1. It is noted that a person having ordinaryskill in the art would recognize that any number of gear reductionassembly designs other than the one illustrated above may be used in theEMTC 84 without departing from the spirit and scope of the invention.

In a number of variations, a torsional wrap spring 140 may surround aportion of the outer circumference of the barrel cam 100 for biasing thebarrel cam 100 to follow rotational movement of the dual drive gear 62,which may allow for completion of range shift movement if temporarilyblocked due to unmeshed gear teeth engagement during axial movement. Thetorsional wrap spring 140 may hold the barrel tab 102 and the dual drivegear actuating tab 64 in radial alignment with each other aftercompletion of rotational driving movement. The torsional wrap spring 140may be constrained to follow movement of the dual drive gear 62 and maybe loaded with force in either rotational direction of the dual drivegear 62. The loaded force of the torsional wrap spring 140 may urgerotational movement of the barrel cam 100 to follow rotational movementof the dual drive gear 62. When the torsional wrap spring 140 is loadedwith force, the torsional wrap spring 140 continually biases the barrelcam 100 in the desired direction of movement until the range shiftmovement is completed. In a number of variations, the barrel cam 100 maybe rotatably biased toward the desired rotational movement by thetorsional wrap spring 140, even if axial movement of the shift fork 116is temporarily blocked while the dual drive gear 62 continues to rotate.If the barrel cam 100 is axially blocked during rotation, the torsionalwrap spring 140 may be loaded with rotational energy to bias the barrelcam 100 to move into a desired orientation when the blocked conditionceases. The torsional wrap spring 140 may store energy between thereverse electric motor 76 and the shift fork 116 until the desired rangemode shift is completed.

In a number of variations, the barrel cam 100 may be interposed betweena first thrust bushing 142 and a second thrust bushing 144. The dualdrive gear 62 may be positioned axially adjacent to the barrel cam 100,the first thrust bushing 142 and one or more ring members 146 which maybe interposed between the barrel cam 100 and the dual drive gear 62. Thedual drive gear 62 may also include a dual drive gear actuating tab 64,as discussed above, which may extend axially toward the range shifter 98and may be radially spaced from the barrel cam 100. The dual drive gearactuating tab 64 may move angularly in either rotational direction(clockwise or counterclockwise) with respect to the barrel tab 102 andmay be independently rotatable from the barrel tab 102.

In a number of variations, the dual drive gear 62 may actuate the rangeshifter 98 through rotational movement of the dual drive gear actuatingtab 64. In a number of variations, when the vehicle 30 is in a low-rangedrive mode, or a high-range drive mode, the shift fork 116 may be in thefirst end portion 110 or the second end portion 112 of the cam groovesurface 108. When the shift fork 116 is in the first or second endportion 110, 112 of the cam groove surface 108, the mode shifter 148 maybe actuated.

Referring to FIGS. 4 and 5, in a number of variations, the mode shifter148 may include a mode cam 150 which may actuate a synchronizer 172. Ina number of variations, the mode cam 150 may be rigidly attached to thedual drive gear 62 so that the mode cam 150 may rotate with the dualdrive gear 62. The mode cam 150 may also include a cam surface groove152 which may extend circumferentially and axially along an innersurface 153 of the inner perimeter of the mode cam 150 and may form awave-like pattern to define an axial travel path for a mode shift fork154 in response to rotation of the mode cam 150 as discussed below. Themode cam 150 may be rotatable about the primary axis 96 through an arcof less than 360 degrees in response to rotation of the dual drive gear62 in either rotational direction.

The mode cam 150 may actuate any number of variations of synchronizers172 including, but not limited to, a single-cone, dual-cone, ortriple-cone synchronizer. In one variation, the synchronizer 172 mayinclude one or more internal rings 174, a blocker ring 176, asynchronizer sleeve 178, a hub 180, and an engagement ring 182. In anumber of variations, the synchronizer sleeve 178 may include a groove184 along an outer surface 186 of the mode sleeve 188 which may beconstructed and arranged to accommodate a second portion 166 of a modeshift fork 154, as will be discussed hereafter.

In a number of variations, a mode shift fork 154 may be operativelyattached to the mode cam 150 and the synchronizer 172 and may be used toshift the vehicle 30 between two-wheel drive and four-wheel drive. Themode shift fork 154 may include a first portion 156 and a second portion166. The first portion 156 may be constructed and arranged tooperatively connect to the mode cam 150 and a mode sleeve 188. The firstportion 156 may include a first and second pin 158 which may extendradially from opposing ends of an outer surface 160 of the first portion156. The pins 158 may be constructed and arranged to travel within themode cam surface groove 152 to allow for axial travel of the mode shiftfork 154 in response to rotation of the mode cam 150. The first portion156 of the mode shift fork 154 may also include a protrusion 162 whichmay extend along a center portion of an inner surface 164 of the firstportion 156 and may be constructed and arranged to rotate within a modesleeve groove 190 in the mode sleeve 188, as will be discussedhereafter. In a number of variations, the second portion 166 may beconstructed and arranged to operatively attach to the synchronizersleeve 178 and may move the synchronizer sleeve 178 axially in responseto rotation of the mode cam 150. The second portion 166 may include aprotrusion 168 on an inner surface 170 of the second portion 166 whichmay be constructed and arranged to sit within a groove 184 in thesynchronizer sleeve 178 so that the synchronizer sleeve 178 is movedaxially in relation to the axial movement of the mode shift fork 154.

In a number of variations, the mode sleeve 188 may extend around thefirst output shaft 86 and may move axially along the first output shaft86. The mode sleeve 188 may be cylindrical and may include a first lip192 and a second lip 194 constructed and arranged to form the modesleeve groove 190 which may accommodate the protrusion 162 on the firstportion 156 of the mode shift fork 154 which may hold the mode shiftfork 154 in place. A wave spring 196 and a snap ring 198 (which may actas a shoulder for the wave spring 196) may be interposed between themode sleeve 188 and the mode shift fork 154. The wave spring 196 mayprovide a tension on the mode sleeve 188 and mode shift fork 154 whichmay assist in moving the mode sleeve 188 and mode shift fork 154 backaxially toward the dual drive gear 62 when the vehicle 30 is shiftedfrom four-wheel drive back to two-wheel drive.

In a number of variations, a first sleeve 202 may be axially adjacent tothe second side 70 of the dual drive gear 62 and may extend within theinner perimeter of the dual drive gear 62 and may be used to rigidly fixthe mode cam 150 to the dual drive gear 62. A portion of the snap ring198 may fit within the inner perimeter of the first sleeve 202. A thrustwasher 204 may sit within a portion of the snap ring 198. A first side208 of a separator thrust washer 206 may lay axially adjacent to thesnap ring 198 and thrust washer 204 and a second side 210 of theseparator thrust washer 206 may lay axially adjacent to the mode cam150. The sprocket 200 may be located axially adjacent to the engagementring 182 of the synchronizer 172.

In a number of variations, when the range shifter 98 is in a low-rangedrive mode or a high-range drive mode, the mode shifter 98 may beactuated to shift the vehicle 30 between the two-wheel drive mode andthe four-wheel drive mode. During a two-wheel drive mode, the firstoutput shaft 86 may rotate within the sprocket 200 without causing thesprocket 200 to rotate. The dual drive gear 62 may be rotated which maycause the mode cam 150 to rotate. This may cause the mode shift fork 154to move axially toward the direction of the sprocket 200 which may causethe engagement ring 182 of the synchronizer 172 to push against andengage the sprocket 200 to cause the sprocket 200 to rotate. The blockerring 176 may prevent the synchronizer sleeve 178 from engaging theengagement ring 182 while the sprocket 200 and the engagement ring 182rotate at different speeds. Once the rotation of the sprocket 200 andthe engagement ring 182 are synchronized, the synchronizer sleeve 178may continue to axially move into a spline engagement with theengagement ring 182 so that the sprocket 200 and the first output shaft86 are operatively attached. The synchronizer 172 may allow forengagement of four-wheel drive quickly by bringing the rotation of thesprocket 200 up to speed with the rotation of the first output shaft 86so that alignment of the teeth on the engagement ring 182 and thesynchronizer sleeve 178 occurs quickly.

The following description of variants is only illustrative ofcomponents, elements, acts, products and methods considered to be withinthe scope of the invention and are not in any way intended to limit suchscope by what is specifically disclosed or not expressly set forth. Thecomponents, elements, acts, products and methods as described herein maybe combined and rearranged other than as expressly described herein andstill are considered to be within the scope of the invention.

Variation 1 may include a transfer case comprising: an input shafthaving a primary axis of rotation; a first output shaft which isconcentric with the input shaft; a second output shaft offset from thefirst output shaft; a range shifter comprising a first cam rotatableabout the primary axis constructed and arranged to selectively shift avehicle to a high-range drive mode, a low range drive mode, or a neutraldrive mode; a mode shifter comprising a second cam rotatable about theprimary axis constructed and arranged to actuate a synchronizer whichselectively shifts the vehicle between a two-wheel drive and afour-wheel drive mode; and a dual drive gear interposed between therange shifter and the mode shifter, wherein a first side of the dualdrive gear includes an actuating tab constructed and arranged to actuatethe first cam and wherein the second cam is attached to a second side ofthe dual drive gear so that the mode shifter is activated by rotation ofthe dual drive gear.

Variation 2 may include a transfer case as set forth in Variation 1further comprising a gear train operatively connected to the dual drivegear to drive the dual gear drive, wherein the gear train has a firstaxis offset from the primary axis; a reversible electric motor whichdrives the gear train in a clockwise and a counterclockwise directionand which has a second axis offset from the primary axis; and anelectronic control unit constructed and arranged to control thereversible electric motor.

Variation 3 may include a transfer case as set forth in any ofVariations 1-2 further comprising a housing surrounding at least aportion of the input shaft, the first output shaft, the second outputshaft, the range shifter, the mode shifter, and the dual drive gear.

Variation 4 may include a transfer case as set forth in any ofVariations 1-3 wherein the range shifter further comprising a springinterposed between the first cam and the dual drive gear which isconstructed and arranged to bias the first cam to follow reversiblerotational movement of the dual drive gear; a shift fork constructed andarranged to travel along a groove in the first cam in response torotation of the first cam; a shift collar constructed and arranged toinclude an axial groove for supporting the shift fork and to allow axialmovement of the shift fork while restricting rotation of the shift fork;and an internal range sleeve operatively connected to the shift fork tomove axially in response to rotation of the first cam.

Variation 5 may include a transfer case as set forth in any ofVariations 1-4 wherein the mode shifter further comprises a shift forkconstructed and arranged to travel along a groove in the mode cam, amode sleeve operatively attached to the shift fork and axially slideableon the first output shaft, a spring interposed between the shift forkand the mode sleeve constructed and arranged to bias the mode sleeve sothat when the vehicle returns to the two-wheel drive mode, the springapplies a force to the mode sleeve to push the mode sleeve back axiallytoward the dual drive gear.

Variation 6 may include a transfer case as set forth in Variation 5wherein the synchronizer includes an engagement ring axially adjacent toa sprocket, wherein the engagement ring is constructed and arranged tomove axially toward the sprocket when the shift fork is moved axiallytoward the sprocket from rotation of the second cam so that thesynchronizer rotates the sprocket to a speed of the first output shaft.

Variation 7 may include a transfer case as set forth in any ofVariations 1-6 further comprising at least one sensing element locatedon a peripheral surface of the dual drive gear for detecting a positionof the dual drive gear; and an electronic control unit for actuating therange shifter and the mode shifter in response to the detected positionof the dual drive gear by the at least one sensing element.

Variation 8 may include a transfer case comprising: an input shafthaving a primary axis of rotation; a first output shaft which isconcentric with the input shaft; a second output shaft offset from thefirst output shaft; a range shifter comprising a first cam, a firstshift fork, wherein the first shift fork is driven axially by the firstcam, and a first sleeve which is axially driven by the first shift fork;a mode shifter comprising a second cam, a second shift fork, wherein thesecond shift fork is driven axially by the second cam, and asynchronizer, wherein the synchronizer is actuated by the second shiftfork through rotation of the second cam; and a dual drive gear, whereinthe dual drive gear is rotated in a forward and a reverse direction toactuate the range shifter and the mode shifter.

Variation 9 may include a transfer case as set forth in Variation 8wherein the range shifter is constructed and arranged to shift a vehiclefrom a low-range drive mode to a high-range drive mode and the modeshifter is constructed and arranged to shift the vehicle from atwo-wheel drive mode to a four-wheel drive mode.

Variation 10 may include a transfer case as set forth in any ofVariations 8-9 further comprising a gear train operatively connected tothe dual drive gear to drive the dual drive gear, wherein the gear trainhas a first axis offset from the primary axis; a reversible electricmotor which drives the gear train in a clockwise and a counterclockwisedirection and which has a second axis offset from the primary axis; andan electronic control unit constructed and arranged to control thereversible electric motor.

Variation 11 may include a transfer case as set forth in any ofVariations 8-10 wherein the dual drive gear further comprises a firstactuating tab constructed and arranged to actuate a first tab on thefirst cam.

Variation 12 may include a transfer case as set forth in any ofVariations 8-11 further comprising a gear reduction assembly, whereinthe first sleeve is engageable between the range shifter and the gearreduction assembly to the first output shaft through a splinedconnection with respect to the first output shaft.

Variation 13 may include a transfer case as set forth in Variation 12wherein the gear reduction assembly further includes a planetary gearset comprising a plurality of planetary gears operatively connected to agear carrier, wherein the plurality of planetary gears rotate within aring gear and are driven by a sun gear.

Variation 14 may include a transfer case as set forth in Variation 13wherein the first cam includes a groove having a low-range portion and ahigh-range portion, and wherein when the first shift fork is driven tothe low-range drive mode portion of the groove, the first sleeve movesaxially to couple the first output shaft with the planetary gear carrierand when the first shift fork is driven to the high-range drive modeportion of the groove, the first sleeve moves axially to couple thefirst output shaft with the sun gear.

Variation 15 may include a transfer case as set forth in any ofVariations 8-14 further comprising at least one sensing element locatedon a peripheral surface of the dual drive gear for detecting a positionof the dual drive gear; and an electronic control unit for actuating therange shifter and the mode shifter in response to the detected positionof the dual drive gear by the at least one sensing element.

Variation 16 may include a transfer case as set forth in any ofVariations 8-15 wherein the synchronizer further includes an engagementring axially adjacent to a sprocket, wherein the engagement ring isconstructed and arranged to move axially toward the sprocket when theshift fork is moved axially toward the sprocket from rotation of thesecond cam so that the synchronizer rotates the sprocket to a speed ofthe first output shaft.

Variation 17 may include a method for assembling a transfer casecomprising: providing an input shaft and a first output shaft coaxiallyon a primary axis of rotation; providing a second output shaft offsetfrom the first output shaft; providing a power transmission deviceinterposed between the first output shaft and the second output shaft;providing a range shifter operatively attached to the first output shaftcomprising a first cam constructed and arranged for shifting between alow-range drive mode, a high-range drive mode, and a neutral drive mode;providing a mode shifter for shift-on-the-fly comprising a second camoperatively attached to a synchronizer constructed and arranged forshifting between a two-wheel drive mode and a four-wheel drive mode;providing a dual drive gear between the range shifter and the modeshifter constructed and arranged so that rotation of the dual drive gearactuates the range shifter and the mode shifter; and providing a geartrain off axis from the primary axis constructed and arranged to drivethe dual drive gear in a clockwise and counter clockwise direction.

Variation 18 may include a method as set forth in Variation 17 furthercomprising an electric motor operatively attached to the gear trainconstructed and arranged for driving the gear train in a clockwise and acounterclockwise direction.

Variation 19 may include a method as set forth in any of Variations17-18 further comprising an electronic control unit operativelyconnected to the electric motor constructed and arranged for controllingoperation of the electric motor.

Variation 20 may include a method as set forth in any of Variations17-19 further comprising at least one sensing element located on thedual drive gear for detecting a position of the dual drive gear; and anelectronic control unit for actuating at least one of the range shifterand the mode shifter in response to the detected position of the dualdrive gear by the at least one sensing element.

The above description of select variations within the scope of theinvention is merely illustrative in nature and, thus, variations orvariants thereof are not to be regarded as a departure from the spiritand scope of the invention.

What is claimed is:
 1. A transfer case comprising: an input shaft havinga primary axis of rotation; a first output shaft which is concentricwith the input shaft; a second output shaft offset from the first outputshaft; a range shifter comprising a first cam rotatable about theprimary axis and constructed and arranged to selectively shift a vehicleto a high-range drive mode, a low range drive mode, or a neutral drivemode; a mode shifter comprising a second cam rotatable about the primaryaxis and constructed and arranged to actuate a synchronizer whichselectively shifts the vehicle between a two-wheel drive mode and afour-wheel drive mode; and a dual drive gear interposed between therange shifter and the mode shifter, wherein a first side of the dualdrive gear includes an actuating tab constructed and arranged to actuatethe first cam and wherein the second cam is attached to a second side ofthe dual drive gear so that the mode shifter is activated by rotation ofthe dual drive gear.
 2. The transfer case of claim 1 further comprisinga gear train operatively connected to the dual drive gear to drive thedual gear drive, wherein the gear train has a first axis offset from theprimary axis; a reversible electric motor which drives the gear train ina clockwise and a counterclockwise direction and which has a second axisoffset from the primary axis; and an electronic control unit constructedand arranged to control the reversible electric motor.
 3. The transfercase of claim 1 further comprising a housing surrounding at least aportion of the input shaft, the first output shaft, the second outputshaft, the range shifter, the mode shifter, and the dual drive gear. 4.The transfer case of claim 1 wherein the range shifter furthercomprising a spring interposed between the first cam and the dual drivegear which is constructed and arranged to bias the first cam to followreversible rotational movement of the dual drive gear; a shift forkconstructed and arranged to travel along a groove in the first cam inresponse to rotation of the first cam; a shift collar constructed andarranged to include an axial groove for supporting the shift fork and toallow axial movement of the shift fork while restricting rotation of theshift fork; and an internal range sleeve operatively connected to theshift fork to move axially in response to rotation of the first cam. 5.The transfer case of claim 1 wherein the mode shifter further comprisesa shift fork constructed and arranged to travel along a groove in themode cam, a mode sleeve operatively attached to the shift fork andaxially slideable on the first output shaft, a spring interposed betweenthe shift fork and the mode sleeve constructed and arranged to bias themode sleeve so that when the vehicle returns to the two-wheel drivemode, the spring applies a force to the mode sleeve to push the modesleeve back axially toward the dual drive gear.
 6. The product of claim5 wherein the synchronizer includes an engagement ring axially adjacentto a sprocket, wherein the engagement ring is constructed and arrangedto move axially toward the sprocket when the shift fork is moved axiallytoward the sprocket from rotation of the second cam so that thesynchronizer rotates the sprocket to a speed of the first output shaft.7. The transfer case of claim 1 further comprising at least one sensingelement located on a peripheral surface of the dual drive gear fordetecting a position of the dual drive gear; and an electronic controlunit for actuating the range shifter and the mode shifter in response tothe detected position of the dual drive gear by the at least one sensingelement.
 8. A transfer case comprising: an input shaft having a primaryaxis of rotation; a first output shaft which is concentric with theinput shaft; a second output shaft offset from the first output shaft; arange shifter comprising a first cam, a first shift fork, wherein thefirst shift fork is driven axially by the first cam, and a first sleevewhich is axially driven by the first shift fork; a mode shiftercomprising a second cam, a second shift fork, wherein the second shiftfork is driven axially by the second cam, and a synchronizer, whereinthe synchronizer is actuated by the second shift fork through rotationof the second cam; and a dual drive gear, wherein the dual drive gear isrotated in a forward and a reverse direction to actuate the rangeshifter and the mode shifter.
 9. The transfer case of claim 8 whereinthe range shifter is constructed and arranged to shift a vehicle from alow-range drive mode to a high-range drive mode and the mode shifter isconstructed and arranged to shift the vehicle from a two-wheel drivemode to a four-wheel drive mode.
 10. The transfer case of claim 8further comprising a gear train operatively connected to the dual drivegear to drive the dual drive gear, wherein the gear train has a firstaxis offset from the primary axis; a reversible electric motor whichdrives the gear train in a clockwise and a counterclockwise directionand which has a second axis offset from the primary axis; and anelectronic control unit constructed and arranged to control thereversible electric motor.
 11. The transfer case of claim 8 wherein thedual drive gear further comprises a first actuating tab constructed andarranged to actuate a first tab on the first cam.
 12. The transfer caseof claim 8 further comprising a gear reduction assembly, wherein thefirst sleeve is engageable between the range shifter and the gearreduction assembly to the first output shaft through a splinedconnection with respect to the first output shaft.
 13. The transfer caseof claim 12 wherein the gear reduction assembly further includes aplanetary gear set comprising a plurality of planetary gears operativelyconnected to a gear carrier, wherein the plurality of planetary gearsrotate within a ring gear and are driven by a sun gear.
 14. The transfercase of claim 13 wherein the first cam includes a groove having alow-range portion and a high-range portion, and wherein when the firstshift fork is driven to the low-range drive mode portion of the groove,the first sleeve moves axially to couple the first output shaft with theplanetary gear carrier and when the first shift fork is driven to thehigh-range drive mode portion of the groove, the first sleeve movesaxially to couple the first output shaft with the sun gear.
 15. Thetransfer case of claim 8 further comprising at least one sensing elementlocated on a peripheral surface of the dual drive gear for detecting aposition of the dual drive gear; and an electronic control unit foractuating the range shifter and the mode shifter in response to thedetected position of the dual drive gear by the at least one sensingelement.
 16. The transfer case of claim 8 wherein the synchronizerfurther includes an engagement ring axially adjacent to a sprocket,wherein the engagement ring is constructed and arranged to move axiallytoward the sprocket when the shift fork is moved axially toward thesprocket from rotation of the second cam so that the synchronizerrotates the sprocket to a speed of the first output shaft.
 17. A methodfor assembling a transfer case comprising: providing an input shafthaving a primary axis of rotation and providing a first output shaftconcentric with the input shaft; providing a second output shaft offsetfrom the first output shaft; providing a range shifter comprising afirst cam rotatable about the primary axis constructed and arranged toselectively shift a vehicle to a low-range drive mode, a high-rangedrive mode, or a neutral drive mode; providing a mode shifter comprisinga second cam rotatable about the primary axis and constructed andarranged to actuate a synchronizer which selectively shifts the vehiclebetween a two-wheel drive mode and a four-wheel drive mode; andproviding a dual drive gear interposed between the range shifter and themode shifter wherein a first side of the dual drive gear includes anactuating tab constructed and arranged to actuate the first cam andwherein the second cam is attached to a second side of the dual drivegear so that the mode shifter is activated by rotation of the dual drivegear.
 18. The method of claim 17 further comprising an electric motoroperatively connected to the dual drive gear constructed and arrangedfor driving the dual drive gear in a clockwise and a counterclockwisedirection.
 19. The method of claim 18 further comprising an electroniccontrol unit operatively connected to the electric motor constructed andarranged for controlling operation of the electric motor.
 20. The methodof claim 17 further comprising at least one sensing element located onthe dual drive gear for detecting a position of the dual drive gear; andan electronic control unit for actuating at least one of the rangeshifter and the mode shifter in response to the detected position of thedual drive gear by the at least one sensing element.